Electronic tuning system with digital band selection

Abstract

The electronic tuning system includes a station selector, a memory, control circuitry, a display and a tuner having the reception band thereof divided into three segments. The tuner incorporates several resonant frequency circuits, each comprising a signal control varactor and a plurality of series connected inductors. Band switching circuitry is provided to simultaneously operatively delete selected inductors from each of the resonant circuits, in accordance with signals generated in a band segment selection circuit. Station selection signals are generated in accordance with the actuation of the signal selector and a display driver circuit is provided to generate a station frequency code to drive the display. The digital band segment selection circuitry generates band segment selection signals in accordance with the station frequency code. The band segment selection circuitry comprises a line decoder, which converts the station frequency code to a decimal number; a plurality of shift registers and bistable circuits which latch the decimal number being multiplexed; and a logic circuit which decodes the decimal number to provide the band segment selection signals to the band switching means.

We claim: 
     
       1. An electronic tuning system or the like comprising: a tuner having a varactor tuned resonant circuit comprising a plurality of series connected inductors and band switching means operably connected to said inductors to operably delete selected ones of said inductors from said resonant circuit in accordance with band segment selection signals; a station selector generating station selection signals in accordance with the actuation thereof; control circuitry operably connected to said station selector and comprising means for generating a varactor control signal in accordance with said station selection signals and means for generating a display code representative of the frequency selected; means for displaying indicia corresponding to said display code; and digital means for generating band segment selection signals, said digital means comprising means for converting said display code into a decimal number and means for decoding said decimal number to form said band segment selection signals. 
     
     
       2. The system of claim 1 wherein said converting means comprises a line decoder and means for inverting the digits of said display code, said decoder receiving, as a first set of inputs, said display code, and as a second set of inputs, the inverted version of said display code, the output of said line decoder forming said decimal number. 
     
     
       3. The system of claim 1 further comprising means for latching said decimal number. 
     
     
       4. The system of claim 2 further comprising means for latching said decimal number. 
     
     
       5. The system of claim 4 wherein said latching means comprises a shift register and a bistable circuit. 
     
     
       6. The system of claim 5 wherein said decoding means comprises a plurality of logic gates. 
     
     
       7. The system of claim 6 wherein said digital means comprises a plurality of monostable circuits connected to receive selected ones of said station selection signals. 
     
     
       8. The system of claim 7 wherein the outputs of said monostable circuits comprise additional inputs to said latching means. 
     
     
       9. The system of claim 1 wherein said varactor control signal generating means comprises means for sensing the frequency to which said resonant circuit is tuned, means for dividing said sensed frequency by a given number, means for generating a reference frequency, means for comparing said reference frequency with the output of said dividing means and means for generating a signal in accordance with the difference between said reference frequency and the output of said dividing means. 
     
     
       10. The system of claim 9 further comprising a memory having stored therein a plurality of data words, each of which corresponds to a different frequency to be tuned. 
     
     
       11. The system of claim 10 further comprising means for addressing said memory in accordance with said station selection signal. 
     
     
       12. The system of claim 11 wherein said given number is selected in accordance with said station selection signal or a selected one of said data words. 
     
     
       13. The system of claim 1 wherein said resonant frequency circuit further comprises an input node, an output node, a plurality of transformers, each having a first transformer winding acting as one of said inductors and a second output link winding, each of said first transformer windings being connected in series, each of said output link windings being connected in series, a fixed capacitance connected in series with said varactor through a first junction to form series connected capacitances, said series connected capacitances being connected in parallel with said series connected first transformer windings, said input node forming a junction between said capacitances and series connected first transformer windings, and said series connected output link windings being connected between said first junction and said output node. 
     
     
       14. The system of claim 13 wherein said resonant circuit forms a portion of the antenna stage of said tuner. 
     
     
       15. The system of claim 14 wherein said resonant circuit has a substantially constant gain throughout each band. 
     
     
       16. The system of claim 8 wherein said resonant frequency circuit further comprises an input node, an output node, a plurality of transformers, each having a first transformer winding acting as one of said inductors and a second output link winding, each of said first transformer windings being connected in series, each of said output link windings being connected in series, a fixed capacitance connected in series with said varactor through a first junction to form series connected capacitances, said series connected capacitance being connected in parallel with said series connected first transformer windings, said input node forming a junction between said capacitance and series connected first transformer windings and said series connected output link windings being connected between said first junction and said output node. 
     
     
       17. The system of claim 16 wherein said resonant circuit forms a portion of the antenna stage of said tuner. 
     
     
       18. The system of claim 17 wherein said resonant circuit has a substantially constant gain throughout each band.